Abstract:
We have studied the effect of topography including ridge and valley on Rayleigh wave
characteristics. A fourth order finite difference method is used for simulations. Gabor
wavelet is used as a source time function. We have computed the seismic response of ridge
and valley with different shape ratio and also by changing the geometry of the topography.
Based on the analysis of simulated results, it is observed that ridge amplify the horizontal
component and de-amplify the vertical component at the crest whereas valley de-amplify
both the horizontal and vertical component. Amplification of horizontal component
increases with increase in shape ratio and also the rate of de-amplification in case of
vertical component increases with increase in shape ratio. Secondly, we have observed that
after the complex interaction of Rayleigh wave with the topography splitting of the wave
occurs and there is time separation between the two splits. One of the split of Rayleigh
wave remain unaffected by the topography and the other passes through the flanks of the
topography. This time separation increases with increase in the shape ratio.
We have also analysed the seismic responses of combinations of various ridge and valley
together. It can be concluded that if Rayleigh wave first interact with the valley rather than
the ridge than the de-amplification occurs and the energy remained in the signal at the last
stations is very negligible. Generally the amplitude of high frequency signal is nearly zero
hence the valley act as a sinking zone for high frequency waves. These combinations are
analysed so that we can relate the hazard associated with it and can recommend the safe
location for building up the houses avoiding landslides, etc.
